UNIT 2 SOLUTION. Q. 1. The vapour pressure of deliquescent substance is less or more than that of water vapours in air?

Size: px

Start display at page:

Download "UNIT 2 SOLUTION. Q. 1. The vapour pressure of deliquescent substance is less or more than that of water vapours in air?"

Marshall Sanders
5 years ago
Views:

1 UNIT 2 SOLUTION 1 MARK QUESTIONS Q. 1. The vapour pressure of deliquescent substance is less or more than that of water vapours in air? Ans. Less than that of water vapours in air. Q. 2. If is the degree of dissociation of Na 2 then write the Vant Hoff factor used for calculating the molecular mass. Ans. i 1 / m 1 (m 1) i (m 1) i i 1 + (3 1) Q. 3. If molecules of urea are present in 100 ml of its soln. then what is the conc. of urea soln.? Ans. N mol molecules mol in 10 ml M N 1000 v 0.01 M Q. 4. Why camphor is used in molecular mass determination? Ans. Because it has very high cryoscopic constant. It has large depression in m. p. when an organic solute is dissolved in it. 1

2 Q M soln of Na 2 is isotonic with 0.01 M soln of glucose at the temp. What is the apparent degree of dissociation of Na 2? Ans. 75% Q. 6. What happen when mango is placed in dilute aqueous soln of HCl? Ans. When mango is placed in dilute aqueous soln. of HCl it swells. Q. 7. Out of (a) 200 ml of 2 M NaCl Soln and (b) 200 ml of 1 M glucose Soln. which one has higher osmotic pressure? Ans. (a) 200 ml of 2 M NaCl Soln. NaCl is an electrolyte which dissolve to give ions. Glucose and urea are non electrolytes. Thus glucose has minimum conc. and hence minimum osmotic pressure. Q. 8. Out of (a) 0.01 M KNO 3 (b) 0.01 M Na 2 which aqueous soln. will exhibit high B. P.? Ans. (a) 0.01 M Na 2 Q. 9. Out of (a) 1 M CaCl 2 (b) 1 M AlCl 3 which aqueous soln. will show max. vapour pressure at 300 K? Ans. (a) 1 M CaCl 3, if we assume 100% dissociation, i for CaCl 2 3 and AlCl 3 4 and relative lowering of V. P. is directly proportional to i. Q. 10. Out of (a) HNO 3 O and (b) C 6 H 6 + C 6 H 5 CH 3 which will form max. boiling azeotrope? Ans. (a) HNO 3 O. 2 MARKS QUESTIONS Q. 1. Two solns of a substance (non-electrolyte) are mixed in the following manner 480 ml of 1.5 M (First Soln) ml of 1.2 M (Second Soln). What is the molarity of the final mixture? 2

3 Ans. Total molarity M V V M V V M Q. 2. To get the hard boiled eggs, why common salt is added to water before boiling the eggs? Ans. Due to addition of common salt the B. P. of the salt containing water elevated, hence the egg at high temp. becomes hard. Q. 3. Equimolal Soln of NaCl and BaCl 2 are prepared in H 2 O. B. F. pt. of NaCl is found to be 2 C. What freezing point do you expect from BaCl 2 soln? Ans. i for NaCl 2 i for BaCl 2 3 T F(NaCl) 2 T (BaCl ) 3 F 2 Therefore T F (BaCl 2 ) T F for BaCl 2 3 C T F 3 C. Q. 4. Why water cannot be separated completely from ethyl alcohol by fractional distillation? Ans. Ethyl alcohol and water (95.4% ethyl alcohol and 4.6% water) form constant boiling mixture (azeotrope) boiling at K. Hence, further water cannot be separated completely from ethyl alcohol by fractional distillation. Q. 5. Why a person suffering from high blood pressure is advised to take minimum quantity of common salt? Ans. Osmotic pressure is directly proportional to the conc. of solutes. Our body fluid contain a number of solutes. On taking large amount of salts, ions enter the body fluid there by raising the conc. of the solutes. As a result osmotic pressure increases which may rapture the blood cells. 3

4 Q. 6. Chloro acetic acid is a monoprotic acid and has K a Calculate b. p. of 0.01 M aqueous soln? (K b 0.51 k kg/mol) Ans. K b 0.51 k kg/mol K a / C / i T b i K b m C Q. 7. Which colligative property is preferred for the molar mass determination of macro molecules? Why? Ans. Osmotic pressure is preferred over all other colligative properties because : (a) (b) even in dil. soln the o. p.values are appreciably high and can be measured accurately. o. p.can be measured at room temp. on the other hand elevation in B. P. is measured at high temp. where the solute may decompose. The depression in freezing point is measured at low temp. Q. 8. How much ethyl alcohol must be added to 1 litre of water so that the solution will freeze at 14 F? (K f for water 1.86 C/mol) Ans. (14 32) / 9 C / 5 C 5 ( 18) / 9 T F 10 C KF 1000 W W M a b b W b mass of solute 4

5 M b molar mass of solute W a mass of solvent Wb W b g Q g of phenol is dissolved in solvent of K F 14, if the depression in freezing point is 7 k. What is the % of phenol? Ans. K F 14 M b 1000 K W W T 1 F F 2 Taking the solvent as 1 kg M b k g per mol phenol (molar mass) 94 g/mol i Calculated molar mass Observed molar mass 94 / C 6 H 5 OH (C 6 H 5 OH) / 2 Total 1 + / 2 1 / 2 5

6 i 1 + / 2 1 / / % of association 75% Q. 10. How many ml of 0.1 M HCl are required to react completely with 1 gm mixture of Na 2 & NaH containing equimolar amounts of both? Ans. Let the amount of Na 2 be x Let the amount of NaH be 1 x Since no. of moles of both are equal x 1 x N(Na CO ) M(NaHCO ) x 1 x x x x XNa / XNaH

7 Na HCl 2 NaCl + CO 2 NaH + HCl NaCl + CO 2 O M 1 V 1 2 M 2 V 2 + M 3 V V V L V ml. 7

Unit - 2 SOLUTIONS VSA QUESTIONS (1 - MARK QUESTIONS) 1. Give an example of liquid in solid type solution.

Unit - 2 SOLUTIONS VSA QUESTIONS (1 - MARK QUESTIONS) 1. Give an example of liquid in solid type solution. 2. Which type of solid solution will result by mixing two solid components with large difference